Composite material comprising bio-filler and specific polymer

ABSTRACT

A composite material comprising 10-98 wt. % of a bio-based particulate or fibrous filler and at least 2 wt. % of a polyester derived from an aliphatic polyalcohol with 2-15 carbon atoms and a polyacid, wherein the polyacid comprises at least 10 wt. % of tricarboxylic acid. 
     Preferably, the filler is in the form of particles, fibers, and/or random or non-random layers. A plant-based filler may be used, in particular a cellulosic or lignocellulosic material, more in particular one or more materials selected from wood chips, wood flakes, sawdust, pulp, e.g., pulp of (recycled) paper or other fiber pulp, and plant-derived fibers such as cotton, linen, flax, and hemp. An animal-derived filler, in particular an animal-derived fiber such as wool, hair, silk, or feathers may also be used. 
     Preferably the polyalcohol is selected from one or more of glycerol, sorbitol, xylitol, mannitol, 1,2-propane diol, 1,3-propane diol, and 1,2-ethane diol, in particular glycerol. The polyacid preferably is an aliphatic diacid or triacid with 3-15 carbon atoms. Examples of suitable acids include citric acid, succinic acid, and itaconic acid. 
     The composite material according to the invention has fire-retardant properties, which makes it particularly suitable for applications where fire-retardancy is an issue.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a § 371 National Stage Application ofPCT/EP2012/056842, filed Apr. 13, 2012, which claims priority toEuropean Application No. 11162428.4, filed Apr. 14, 2011, U.S.Provisional Application No. 61/475,431, filed Apr. 14, 2011, EuropeanApplication No. 11162445.8, filed Apr. 14, 2011, and U.S. ProvisionalApplication No. 61/475,411, Apr. 14, 2011.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention pertains to a composite material comprising afiller and a specific polymer. More in particular, the present inventionpertains to a composite material comprising a bio-based particulate orfibrous filler and a specific polymer.

Description of Related Art

Composite materials comprising bio-based particulate or fibrous fillersare well known in the art. They include, for example, compositematerials comprising plant-based fillers, such as MDF (medium densityfiberboard), HDF (high-density fiberboard), plywood, oriented standboard (OSB) also indicated as flake or wafer board, particle board andpaper-resin composites like Formica™. These materials comprise aplant-based particulate or fibrous filler in combination with a polymerto keep the material together.

Conventional polymers used in the manufacture of these types ofcomposite materials have a number of disadvantages. Depending on theirnature, they may cause the slow release of formaldehyde, compositematerials containing them cannot be disposed of as organic waste, andwhen burned they may cause the release of undesirable components. Thepresent invention now provides a composite material which solves theseproblems.

SUMMARY

The present invention pertains to a composite material comprising 10-98wt. % of a bio-based particulate or fibrous filler and at least 2 wt. %of a polyester derived from an aliphatic polyalcohol with 2-15 carbonatoms and polyacid, wherein the polyacid comprises at least 10 wt. % oftricarboxylic acid.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The polyester used in the present invention does not contain aromaticstructures or N or S heteroatoms. More in particular, it consistsessentially of carbon, hydrogen, and oxygen atoms.

It therefore shows a clean burning profile, a good HSE profile, and isalso suitable for disposal as organic waste.

In contrast with composite materials based on conventional polymers, thecomposite material according to the invention can therefore be disposedof as organic waste.

The polymer slowly hydrolyzes in water. Thus, when the compositematerial is used as land-fill, the polymer will slowly degrade, makingthe bio-based particulate or fibrous filler available for biologicaldegradation.

It has also surprisingly been found that the composite materialsaccording to the invention show a high fire resistance. This makes thecomposite material according to the invention eminently suitable asbuilding material and in other applications where fire-resistance is anissue. The composite according to the invention thus combines goodtechnical properties with good disposal properties.

Another advantage is that the polymer used in the composite according tothe invention may be derived in its entirety from renewable vegetableresources. It does not have to rely on fossil fuels.

Another advantage is that the composite according to the invention maybe derived in its entirety from renewable bio-derived resources, inparticular vegetable resources. It does not have to rely on fossilfuels.

The bio-based particulate or fibrous material is present in thecomposite material according to the invention as filler. If the amountof filler is less than 10 wt. %, a composite material with the desiredproperties may be difficult to obtain. If the amount of filler is above98 wt. %, the amount of matrix polyester will be too low to provide theproduct with adequate properties.

In one embodiment, the filler is present in an amount of at least 20 wt.%, in particular at least 40 wt. %, more in particular at least 50%. Insome embodiments, the amount of filler may be at most 95%, more inparticular at most 90%.

The polyester is present in an amount of at least 2 wt. %. It may bepreferred for the polyester to be present in an amount of at least 5 wt.%, still more in particular at least 10 wt. %.

The amount of polyester will be below 80 wt. %, because otherwise theamount of filler will be too low.

The filler is a bio-based particulate or fibrous filler. Within thecontext of the present specification the word bio-based refers tofillers which are derived from plant- or animal-based materials.Combinations of different types and materials of fillers may also beused.

In one embodiment the filler is a plant-based particulate or fibrousfiller. In this case the filler may be a cellulosic or lignocellulosicmaterial.

The filler may be in the form of individual particles or fibers, butalso in the form of an aggregate material, e.g., in the form of woven ornon-woven layers.

Within the context of the present specification the wording fiberencompasses monofilaments, multifilament yarns, threads, tapes, strips,and other elongate objects having a regular or irregular cross-sectionand a length substantially longer than the width and thickness.

In one embodiment, the fiber-type filler is in the form of a poroussheet-like material, e.g., in the form of a sheet wherein the fibers areoriented in a random or non-random manner.

In one embodiment the fibers are oriented in the layer in a randommanner, e.g., in a non-woven sheet.

In another embodiment the fibers are oriented in a non-random manner. Inthe context of the present specification the wording oriented in anon-random manner is intended to refer to all structures wherein fibersare connected to each other in a more or less regular manner. Examplesinclude woven layers, knitted layers, layers wherein the fibers areoriented in parallel, and any other layers wherein fibers are connectedto each other in a repeating pattern. Examples of suitable materials arewoven or non-woven layers of, e.g., cotton or linen.

In one embodiment, the layers have a mesh width in the range of 0.01 to5 mm.

In another embodiment, the filler is based on a particulate material,e.g., in the form of powder, dust, pulp, broken fibers, flakes, orchips. Examples include wood chips, wood flakes, and sawdust, and pulp,e.g., pulp of (recycled) paper or other fiber pulp.

In another embodiment the filler is based on plant-derived fibers.Examples include cotton, linen, flax, hemp, etc.

The filler may also be based on animal-derived fillers, in particular onanimal derived fibers such as wool, hair, and silk, and fibers derivedfrom feathers, e.g., chicken feathers. Where suitable, other parts ofoffal may also be used.

It may be preferred for the filler to have a fibrous character orplatelike character, e.g. as evidenced by the aspect ratio between thelargest dimension, the length, and the smallest dimension, thethickness, being at least 3, in particular at least 5. In someembodiments the aspect ratio may be at least 10, or even higher. It isbelieved that the use of material with a fibrous or plate-like characterwill lead to a material with improved directional properties, e.g.,increased strength.

The composite according to the invention may be obtained by combiningthe filler with the polymer or precursor thereof, and subjecting thecombination to a curing step.

The combining of the filler with the polymer or precursor thereof may becarried out in various manners, depending on the type and amount offiller and polymer.

In one embodiment the polymer or precursor thereof is in liquid form.

In one embodiment, the filler is mixed through the liquid usingconventional mixing apparatus. In another embodiment, the filler isbrought into a mould and the liquid is applied onto the filler in themould. In a further embodiment the composite material is a laminatewhich can be obtained, for example, by coating or impregnating theindividual layers with a polymer or precursor thereof in liquid form. Inall cases, the resulting combination of filler and liquid polymer issubjected to a curing step until a solid composite is obtained.

Combinations of different methods, e.g., combinations of laminates andmixed materials are also envisaged.

In one embodiment, the filler is combined with monomers in the liquidphase, and the combination is subjected to a curing step until a solidcomposite is obtained.

As indicated above, in another embodiment, the polyalcohol and polyacidare combined and subjected to polymerization conditions to form apolymer in liquid form. The liquid polymer is then combined with thefiller, and the combination is subjected to a curing step until a solidcomposite is obtained.

In this embodiment the starting material is a polymer with a degree ofpolymerization which is such that the polymer is still liquid. In thisspecification, the liquid polymer which will later be combined with thefiller may also be indicated as prepolymer.

In making the prepolymer the polymerization is carried out to such anextent that a liquid polymer is formed the viscosity of which is suchthat the filler material can be incorporated therein without miscibilityproblems. Optionally, the polymer may be heated to reduce its viscosity.It is within the scope of the skilled person to determine a suitableviscosity, taking the particular type of mixing, the nature and amountof filler, and the nature and amount of polymer into account.

If so desired, a solvent may be present in the reaction mixture duringthe manufacture of the prepolymer to result in a less viscous product.Solvent may be present, for example, in an amount of 5-50 wt. %,calculated on the total of polymer and solvent, in particular in anamount of 5-20 wt. %. Although other polar solvents can also be used,the use of water is preferred for environmental and cost reasons.

In general, the prepolymerisation may be carried out at a temperature inthe range of 20 to 200° C., preferably in the range of 40 to 150° C.,more preferably in the range of 40 to 130° C. The reaction may becarried out at atmospheric pressure, but if so desired also at higher orlower pressures.

The degree of polymerization for the prepolymer may be in the range of20 to 98 wt. % (calculated on the basis of the weight loss of themixture), in particular in the range of 40 to 98 wt. %, or in the rangeof 20-50 wt. %. The degree of prepolymerisation will depend on thedesired viscosity and on the further polymerization steps.

In another embodiment, the composite according to the invention may beobtained by combining the filler with a pre-polymer in the solid phase,and subjecting the combination to temperature and pressure to in thefirst instance melt the polymer to allow bonding to the filler, and thenallow further polymerization of the polymer to solidify the material. Inthis embodiment, the polymer may be provided, e.g., as particles or asfilms.

In the following, the polymerization reaction will be discussed. Exceptwhere indicated otherwise the following is applicable both to thepolymerization carried out in the presence of filler and to thepolymerization in the absence of filler, i.e., in the manufacture of theprepolymer.

The starting materials for the present invention are an aliphaticpolyalcohol with 2-15 carbon atoms and a polyacid, wherein the polyacidcomprises at least 10 wt. % of tricarboxylic acid.

The polyalcohol used in the present invention does not contain aromaticstructures or N or S heteroatoms. More in particular the polyalcohol isan aliphatic polyalkanol containing only C, H, and O atoms. Thepolyalcohol used in the present invention comprises at least twohydroxyl groups, in particular at least thee hydroxyl groups. Ingeneral, the number of hydroxyl groups will be 10 or less, more inparticular 8 or less, or even 6 or less.

The polyalcohol has 2-15 carbon atoms. More in particular, thepolyalcohol has 3-10 carbon atoms.

It is preferred for the polyalcohol to contain no other non-carbongroups than hydroxyl groups. It is preferred for the alcohol to containno heteroatoms, including oxygen, in its backbone.

In a preferred embodiment of the present invention the polyalcoholcontains a relatively large number of hydroxyl groups in comparison withits number of carbon atoms. For example, the ratio between the number ofhydroxyl groups and the number of carbon atoms ranges from 1:4 (i.e. onehydroxyl group per four carbon atoms, or 8 carbon atoms for a dialcohol)to 1:0.5 (i.e. 2 hydroxyl groups per carbon atom). In particular, theratio between the number of hydroxyl groups and the number of carbonatoms ranges from 1:3 to 1:0.75, more specifically, from 1:2 to 1:0.75.A group of specifically preferred polyalcohols is the group wherein theratio ranges from 1:1.5 to 1:0.75. Compounds wherein the ratio ofhydroxyl groups to carbon atoms is 1:1 are considered especiallypreferred.

Examples of suitable polyalcohols include glycerol, sorbitol, xylitol,and mannitol, and, from the group of dialcohols 1,2-propane diol,1,3-propane diol, and 1,2-ethane diol. The use of compounds selectedfrom the group of glycerol, sorbitol, xylitol, and mannitol, ispreferred, with the use of glycerol being particularly preferred.

The preference for glycerol is based on the following: In the firstplace glycerol has a melting point of 20° C., which allows easyprocessing, in particular as compared to xylitol, sorbitol, andmannitol, which all have melting points well above 90° C. Further, ithas been found that glycerol gives a polymer of high quality, and thuscombines the use of an easily accessible source material with goodprocessing conditions and a high-quality product.

Mixtures of different types of alcohol may also be used.

It is preferred, however, for the alcohol to consist for at least 50mole % of glycerol, xylitol, sorbitol, or mannitol, in particular ofglycerol, preferably at least 70 mole %, more in particular at least 90mole %, or even at least 95 mole %. In one embodiment the alcoholconsists essentially of glycerol.

The use of glycerol which is a side product of the manufacture ofbiodiesel by the transesterification reaction of glycerides withmono-alcohols is a specific embodiment of the present invention.Suitable monoalcohols include C1-C10 monoalcohols, in particular C1-C5monoalcohols, more in particular C1-C3 monoalcohols, specificallymethanol. The glycerides are mono- di- and esters of glycerol and fattyacids, the fatty acids generally having 10-18 carbon atoms. Suitableprocesses for manufacturing biodiesel with associated glycerol are knownin the art.

The polyacid does not contain aromatic structures or N or S heteroatoms.More in particular the polyacid is an aliphatic polycarboxylic acidcontaining only C, H, and O atoms. It is preferred for the polyacid tocontain no other functional groups than carboxylic acid groups. It ispreferred for the acid to contain no heteroatoms, including oxygen, inits backbone.

The polyacid comprises at least 10 wt. % of tricarboxylic acid, whetheror not in combination with dicarboxylic acids, other tricarboxylicacids, and mixtures thereof.

In one embodiment the acid comprises at least 30 wt. % of tricarboxylicacid, calculated on the total amount of acid, preferably at least 50 wt.%. In one embodiment the amount of tricarboxylic acid is at least 70 wt.%, more in particular at least 90 wt. %, or even at least 95 wt. %. Inone embodiment the acid consists essentially of tricarboxylic acid,wherein the word essentially means that other acids may be present inamounts that do not affect the properties of the material.

In one embodiment the acid comprises at least 10 wt. % of dicarboxylicacid, calculated on the total amount of acid, preferably at least 30 wt.%, more preferably at least 50 wt. %.

In one embodiment the amount of dicarboxylic acid is at least 70 wt. %.

In one embodiment the acid comprises a combination of at least 10 wt. %of tricarboxylic acid and at least 2 wt. % of dicarboxylic acid, more inparticular at least 10 wt. % of tricarboxylic acid and at least 5 wt. %of dicarboxylic acid, or at least 10 wt. % of tricarboxylic acid and atleast 10 wt. % of dicarboxylic acid. In this embodiment the weight ratiobetween the two types of acid may vary within wide ranges, depending onthe properties of the desired material. In one embodiment, thedicarboxylic acid makes up between 2 and 90 wt. % of the total ofdicarboxylic and tricarboxylic acid, in particular between 5 and 90 wt.%, more in particular between 10 and 90 wt. %, depending on theproperties of the desired material. It is noted that the preferredranges for the tricarboxylic acid specified above are also applicable tothis embodiment.

It has been found that the use of a tricarboxylic acid, in particularcitric acid, results in the formation of a high-quality compositematerial, in particular in combination with the use of a trialcohol suchas glycerol. Not wishing to be bound by theory we believe that there area number of reasons why the use of a tri-acid, in particular incombination with a tri-ol results in the formation of a high-qualitycomposite material. In the first place, the use of a tri-acid, inparticular in combination with a tri-ol, makes for a highly crosslinkedpolymer, resulting in increased strength. Further, where a tri-acid, andpreferably also a tri-ol is used, there is a large possibility of acidor hydroxyl groups to physically or chemically interact with activegroups on the filler. This leads to improved bonding between the fillerand the polymer, which is a key desire in creating composite materials.The degree of interaction can be controlled by selection of the amountof triacid and trialcohol, and by selecting the degree ofpolymerization. It is noted that this is a key difference withcomposites based on di-acids polymerised with di-ols.

The dicarboxylic acid, if used, may be any dicarboxylic acid which hastwo carboxylic acid groups and, in general, at most 15 carbon atoms.Examples of suitable dicarboxylic acids include itaconic acid, malicacid, succinic acid, glutaric acid, adipic acid and sebacic acid.Itaconic acid and succinic acid may be preferred.

The tricarboxylic acid may be any tricarboxylic acid which has threecarboxylic acid groups and, in general, at most 15 carbon atoms.Examples include citric acid, isocitric acid, aconitic acid (both cisand trans), and 3-carboxy-cis,cis-muconic acid. The use of citric acidis considered preferable, both for reasons of costs and of availability.The citric acid can be provided in anhydrous form. However, as thepresence of water is not detrimental to the process, it is possible, andpreferred to use citric acid monohydrate as starting material.

The molar ratio between the polyalcohol and the polyacid will begoverned by the ratio between the number of reacting groups in thealcohol(s) and acid(s) used.

In general, the ratio between the number of OH groups and the number ofacid groups is between 5:1 and 1:5. More in particular, the ratio maybetween 2:1 and 1:2, more specifically between 1.5:1 and 1:1.5, morepreferably between 1.1:1 and 1:1.1. The theoretical molar ratio is 1:1.

The alcohol and the acid are combined to form a liquid phase. Dependingon the nature of the compounds this can be done, e.g., by heating themixture to a temperature where the acid will dissolve in the alcohol, inparticular in glycerol. Depending on the nature of the compounds thismay be, e.g., at a temperature in the range of 20-200° C., e.g., 40-200°C., e.g. 60-200° C., or 90-200° C. In one embodiment, the mixture may beheated and mixed for a period of 5 minutes to 2 hours, more specifically10 minutes to 45 minutes, at a temperature of 100-200° C., in particular100-150°, more in particular at a temperature in the range of 100-130°C.

If a solvent is added, e.g., water, the temperature may be lower, e.g.,in the range of 40° C. or higher, e.g., at a temperature of 40-100° C.,in particular 50-100° C., because the water will help to dissolve theacid in the alcohol, in particular glycerol. In this embodiment, themixture may be heated and mixed for a period of 5 minutes to 2 hours,more specifically 10 minutes to 45 minutes, at a temperature in thespecified range.

If so desired, a polymerisation catalyst may be added to the reactionmixture. Suitable catalysts for polyester manufacture are known in theart. They include, e.g., p-toluene sulphonic ester and tin oxalate, andsulphuric acid. It is within the scope of the skilled person to select asuitable catalyst.

It has been found, however, that the use of a catalyst is generally notrequired.

The polymer aimed for is the reaction product of polyalcohol andpolyacid. Other components may be present in the reaction medium, butpreferably not to an extent that they substantially interfere with thenature of the reaction product. Suitable components that may be presentinclude catalysts and colorants. In one embodiment less than 20 wt. % ofthe reaction mixture should be made up of other components, preferablyless than 15 wt. %, more preferably less than 10 wt. %. In someembodiments it may be preferred for the mixture to contain less than 5wt. % of additional components, or even less than 2 wt. %. The abovepertains to components which end up in the final product. For example,water or other solvents which are evaporated from the final product andother gaseous components that may be added, if any, are not includedherein. The filler and other solid constituents are also not taken intoaccount in the calculations in this paragraph.

The liquid mixture comprising alcohol and acid is brought to reactionconditions. Reaction conditions include a temperature of between 20° C.and 200° C., in particular The reaction temperature will depend on thedesired reaction time and the presence or absence of a catalyst. In oneembodiment the reaction temperature is between 50 and 150° C., inparticular between 80 and 130° C. An increased temperature will resultin an decreased reaction time. The selection of a higher temperaturewithin the stipulated range will increase reaction rate, but will alsoincrease the risk of undesirable side reactions such as decarboxylation.Taking the above into account it is within the scope of the skilledperson to select a proper reaction temperature.

In one embodiment, the polymer is a glycerol-tricarboxylic acidpolyester, in particular a glycerol citric acid polyester, with a carboncontent of at most 43.00 wt. % and a hydrogen content of at most 5.40wt. %.

In the process according to the invention the combination of the fillerwith the polymer or a precursor thereof is subjected to a treatment atelevated temperature and pressure until the polymer has solidified.

The solidification of the polymer generally means that the mixture hasreached a degree of polymerization of at least 70%, in particular atleast 80%, more in particular at least 90%, in some embodiments at least95%.

It is preferred that the combination of polymer and filler is subjectedto a temperature in the range of 20-200°, in particular 40-150° C., morein particular 80-130° C. and a pressure of 1-100 bar, in particular 2-50bar, more in particular 2-20 bar, for a period of at least 5 minutes,until the polymer has solidified. For further preference on reactiontimes and temperatures reference is made to what is stated elsewhere inthis document.

In one embodiment the temperature of the reaction mixture is notelevated above 130° C. before a conversion of at least 90% has beenobtained. This may be attractive to prevent decomposition of the acidwhich may cause discoloration of the product and may affect theproperties of the polymer. It is preferred that the temperature of thereaction mixture is not elevated above 130° C. before a conversion of atleast 95% has been obtained, more in particular a conversion of at least98%. It is believed that when the reaction is complete or substantiallycomplete, the polymer will tolerate higher temperatures, because at thatpoint in time the acid has already been polymerized, reducing the riskof decarboxylation. For example, it has been found that when the desireddegree of conversion is reached, the polymer can be heated further to atemperature of, e.g., 150° C. without further problems. This means thatit can be used in many industrial and technological applications. In oneembodiment it is preferred for the temperature of the reaction mixtureto be not elevated above 125° C. before a conversion of at least 90% hasbeen obtained. A maximum temperature of 120° C. may be more preferred.It is also preferred that temperatures above these values are notreached before a conversion of at least 95% has been obtained, more inparticular a conversion of at least 98%.

In one embodiment it is preferred for the reaction to be carried out forat least part of the time above the boiling point of water, that is,above the point where the vapor pressure of the liquid equals theenvironmental pressure surrounding the liquid. When the reaction iscarried out at atmospheric pressure it is therefore preferred for thereaction to be carried out at a temperature above 100° C., more inparticular at 105° C. or higher. When the reaction is carried at reducedpressure within this embodiment, the reaction may be carried out atlower temperatures, e.g., a temperature of between 80° C. and 100° C. ata pressure of 0.10 mbar.

The polymerization time will depend on the polymerization temperatureand desired degree of polymerization, and may vary between wide ranges.In one embodiment, the polymerization time is between 5 minutes and 5days. In the presence of catalyst at elevated temperatures thepolymerization time could, e.g., be in the range of 5 minutes to 12hours, more in particular 0.5 hours to 6 hours. The polymerization timemay also be at least 1 hour, or at least 2 hours, or at least 4 hours.In one embodiment, the polymerization time in the range of 2 hours to 5days, in particular 2 hours to 24 hours, more in particular in the rangeof 4 to 18 hours, still more in particular in the range of 8-20 hours.

Combinations of various temperature and pressure regimens may beenvisaged.

In one embodiment the reaction mixture is kept at a temperature ofbetween 100° C. and 130° C. for at least part of the period from thestart of the reaction until a conversion of at least 90% is obtained.More specifically, it may be desirable to keep the reaction mixture at atemperature of between 100° C. and 130° C. for the entire period fromthe start of the reaction until the desired degree of conversion isobtained.

In one embodiment, the alcohol and acid are mixed at a temperature of50-200° C. for a period of 5 minutes to one hour. The filler is added,and the mixture is then poured into a mould and kept there at atemperature of 50-200° C., in particular 80-150° C., more in particular90-150° C. for a period of 0.5 hours to 5 days hours, in particular 2-36hours.

In another embodiment, alcohol and acid are mixed with water in anamount of, say 2-10 wt. %, calculated on the total of acid at atemperature in the range of 40-100° C., in particular 40-80° C. for aperiod of 5 minutes to one hour. The filler is added, and the mixturecan then by poured in the mould and processed as described above.

In one embodiment the prepolymer is at elevated temperature when it iscombined with the filler, e.g., at a temperature of above 60° C., inparticular above 80° C. In one embodiment the temperature is between 100and 150° C. The advantage of the prepolymer having a relatively hightemperature when it is combined with the filler is that it allowsprocessing of a polymer with a relatively high degree of polymerizationat acceptable viscosity. This ensures that the curing step of the finalcomposite can be relatively short.

The rate of the polymerization may be increased by seeding the mixturewith pulverized polymer, e.g., in an amount of 1-20 wt. %. This isbelieved to result in a material with a lower density.

It has been found that the polymers shows strong adherence to glass andmetal. The final stages of the polymerization reaction, including theheat and pressure treatment of polymer and filler, are thereforepreferably carried out in a vessel provided with a non-stick coating.This can be, for example, a Teflon coating, or a silicone rubbercoating. Suitable coating materials are known in the art.

It may be preferred for the mixing and reaction stage to take place inan inert atmosphere, e.g., under nitrogen or argon, to prevent reactionof the polymer or the monomers with the oxygen from the air, which mayresult in yellowing of the polymer.

The polymer used in the present invention will slowly hydrolyze whenbrought into contact with water. The hydrolyzation speed will depend inthe degree of polymerization. Accordingly, if a certain degree ofdegradability is desired, e.g., in packaging applications a lower degreeof polymerization may be selected, e.g., between 70 and 90%. However, incases where a more stable material is desired, with a longer degradationtime, a higher degree of polymerization may be more attractive. In thiscase, a degree of polymerization of more than 90%, e.g., of at least93%, at least 96%, or at least 98% may be aimed for.

In general, the materials with a lower degree of conversion will be moreflexible than materials with a higher degree of conversion.

If so desired, the composite material according to the invention mayencompass additional polymers. In one embodiment it may be preferred forthese polymers to be degradable and/or based on biomaterials. Examplesof suitable polymers include polymers derived from lactic acid, glycolicacid, cellulose, and bioethanol.

It is preferred for the material according to the invention to be freeof epoxyresins and other resins containing N- and S-heteroatoms. In oneembodiment, the composite material according to the invention containsless than 5 wt. % of epoxyresin, in particular less than 2 wt. % ofepoxyresin.

In one embodiment the polymer used in the present invention containsless than 10 wt. % of compounds containing other atoms than O, C, or H.

The composition may contain additional components. Examples includeinert fillers like ash, carbon, silica (sand), titania, and other inertmaterials.

The composite material may be in the form of a shaped body. Examples ofshaped bodies include plates, extrudates, and any otherthree-dimensional shapes that can be derived from a mould.

In one embodiment the present invention pertains to a panel made fromthe composite material of the present invention. The panel may have,e.g. a thickness in the range of 1 mm to 4 cm, in particular of 2 mm to2.5 cm. The plate may have a width of 10 cm to 3 m, in particular 20 cmto 2 m. The length of the panel may, e.g., be in the range of 30 cm to 5meter, in particular 1 meter to 4 meter. The plates may also havecircular or irregular shapes.

In another embodiment, the present invention pertains to a complexshaped object, i.e. and object which is not flat. Such complex shapedobjects can be used for numerous applications.

The composite materials according to the invention have many uses.

It has been found that the composite material of the present inventionis particularly attractive in applications where fire-hazards may exist.

Fire is a hazard which may occur in many locations, from the home tovehicles such as trains, planes, ships, trucks, and passenger cars,offices, factories, tunnels, and open locations. To prevent the risksassociated with fire, flame-retardant materials are used in manylocations. To improve the flame retardancy of a material, flameretardant additives are often incorporated therein. Such additivesinclude halogenated flame-retardants containing, e.g., bromine,chlorine, or iodine, metal hydrates, and nitrogen and phosphorus-basedflame retardants. It has been found, however, that these flame retardantadditives may in themselves constitute a HSE risk. This goes inparticular for the halogen-containing compound such as thebromine-containing compounds.

Thus, there is a need in the art for materials which catch fire onlyslowly, may show self-extinguishing properties, or may not catch fire atall. Such a material may be useful in many applications where theproliferation of fire is to be prevented. It has been found that thespecific polyester used in the composite material of the presentinvention, and therewith the composite material itself, have goodflame-retardant properties. More in particular, the composite materialdoes not easily catch fire, may shows self-extinguishing properties, andmay not catch fire at all.

The use of the specified composite material comprising the specifiedpolyester makes it possible to reduce the content of flame-retardantadditives such as halogenated flame-retardants, metal hydrates, andnitrogen and phosphorus-based flame retardants. Depending on theapplication, the use of the specified polyester may even make itpossible to dispense with the use of flame-retardant additives such ashalogenated flame-retardants, metal hydrates, and nitrogen andphosphorus-based flame retardants altogether.

The present invention thus also pertains to a kit of parts comprising apart susceptible to degradation by thermal loads and a part comprisingflame retardant part. The kit of parts of the present invention hasnumerous further advantages, which will become apparent from the furtherspecification.

The present invention pertains to a kit of parts comprising a partsusceptible to degradation by thermal loads and a part comprising thecomposite material of the present invention, which comprises 10-98 wt. %of a synthetic particulate or fibrous filler and at least 2 wt. % of apolyester derived from an aliphatic polyalcohol with 2-15 carbon atomsand polyacid, wherein the alcohol comprises at least 50 mole % ofglycerol, and the acid comprises at least 50 wt. % of tricarboxylicacid.

It has been found that the specific polyester used in the presentinvention shows good flame retardant properties. Additionally, it may inmany applications be used without further flame retardant additives, inparticular halogen-containing compounds, more in particularbromine-containing compounds, being required.

The wording “part susceptible to thermal loads” encompasses everythingwhich, when subjected to fire or heat, suffers from degradation. Theymay, for example, burn, explode, melt, or suffer from a decrease infunctional properties, e.g., mechanical properties.

The wording “kit of parts” as used within the present specificationshould be interpreted broadly. It encompasses a combination of a partsusceptible to thermal loads and a part comprising the compositematerial according to the invention wherein the kit is providedtogether, e.g., in the situation wherein the two parts of the kit ofparts are connected to form a single object, e.g., a televisioncomprising a screen (the part susceptible to thermal loads) and a casingcomprising the composite material. It also encompasses the situationwherein the part susceptible to thermal loads and the part containingthe composite material are provided separately, e.g., in the situationwhere the part containing the composite material is combined with thepart susceptible to thermal loads at the location of use, e.g., the useof panels comprising the polyester in a tunnel or building. In thelatter case, it is not necessary to the parts to be combined in apermanent manner. The invention also provides for the situation whereinthe kit of parts exists only temporarily.

In one embodiment the present invention pertains to an assemblycomprising a part susceptible to degradation by thermal loads and acover surrounding said part in whole or in part, wherein the covercomprises the composite material comprising the specified polyester.

The word cover in the present specification should be interpretedbroadly. It encompasses housings surrounding a part susceptible tothermal loads, but it also encompasses shielding that may be placedbetween the possible fire location and the part susceptible to thermalloads.

An example of an assembly according to the invention is electronicapparatus provided with a casing, e.g., computers, televisions and otherscreens, audio and video apparatus, etc. In this embodiment thatinvention pertains to an electronic apparatus comprising electronicparts susceptible to thermal loads and a casing comprising the specifiedcomposite material.

A further example of a kit of parts or assembly according to theinvention is a building structure provided with a panel comprising thespecified composite material. Examples of building structures includehomes, offices, factories, tunnels, and bridges.

Examples of panels include paneling for walls, floors, ceilings, doors,and shutters.

The present invention thus also pertains to panels comprising thespecified composite material which are provided with fastening means forapplication in building structures.

A further example of an assembly according to the invention is a vehicleprovided with a panel comprising the specified composite material.Panels may encompass, e.g., panels used in interiors of trains, planes,ships, trucks, and passenger cars. Examples include dashboard panels,side panels, shelves, seats and seat covers, fuel tanks and fuel tankshielding, etc.

In one embodiment, the properties of the flame retardant part are suchthat the time-to-degradation of the part susceptible to thermal loads isincreased with at least 10% as compared to the situation where the partis subjected to a thermal load in the absence of a cover or casing. Inparticular, the time-to-degradation is increased with at least 30%, morein particular at least 50%, even more in particular at least 100%. Theincrease in time-to-degradation may in one embodiment be at least 200%,or at least 300%, or at least 400%.

In one embodiment the flame retardant part is substantially free frombromine-containing flame-retardant additives. In one embodiment theflame retardant part is substantially free from halogen-containingflame-retardant additives. In a further embodiment, the flame retardantpart is substantially free from halogen-, nitrogen, orphosphorus-containing flame-retardant additives. In this context theword substantially free means that the compound is not added on purpose,and only present in amounts which cannot be avoided.

The present invention also pertains to a part and cover as describedabove.

The present invention also pertains to the use of the specifiedcomposite material as flame retardant material. In one embodiment, anintermediate product comprising said polyester is applied as a flameretardant material. The invention also pertains to said intermediateproduct.

The invention also pertains to a method for decreasing thefire-propagating properties of a system comprising incorporating thereina part comprising a composite material comprising the specifiedpolyester. The invention also pertains to a fire protecting covercomprising the specific composite material comprising said polyester. Inone embodiment, the cover is intended for protecting the human or animalbody.

The present invention is illustrated by the following non-limitingexamples.

Example 1—Composite Based on Paper Pulp

Glycerol (8 grams) and citric acid monohydrate (16 grams) were heatedwith 20 ml of demineralized water in an open beaker at 60° C. for 20minutes. A homogeneous solution was obtained.

Paper pulp was prepared from 8 grams Kimberley Clark cellulose wipes ina mechanical blender with 200 ml water for 30 minutes. The polymersolution was added to the mush and blended for 20 minutes. Theimpregnated mush was cast in a silicone rubber mould (10*20*5 cm3) andcured at 120° C. for 12 hrs under a flow of nitrogen. A coherentcomposite material was obtained (dimensions 10*12*0.5 cm).

Example 2—Composite Based on Sawdust

Citric acid monohydrate (18 grams) and glycerol (9 grams) were heated to100° C. for 15 minutes with stirring in an open beaker until ahomogeneous solution was obtained.

Epoxy-free sawdust (8 grams) was added in portions with manualstirring/mixing with a steel spatula until a thick paste was obtained.The sawdust paste was cured in a silicone rubber cup (5 cm diameter) at120° C. for 12 hrs. A porous brown fiber board (0.7 cm height) resultedwith density lower than 1 g/ml.

Example 3—Composite Based on Sawdust

A sawdust paste was prepared as described in Example 2. The sawdustpaste was spread out on a silicone rubber sheet. A second siliconerubber sheet was placed on top and the paste was cured under pressure ofa 2 kg stone at 120° C. for 12 hrs. A porous brown coherent fiber board(7*8 cm and 0.5 cm thickness) was obtained with a density above 1 g/ml.

Example 4—Composite Based on Sawdust

A sawdust paste was prepared as described in Example 2. The paste wasplaced between two silicone rubber sheet and heated at 120° C. under 10bars pressure. A thin sheet of brown medium density fiber board wasobtained (7*10 cm and 1 mm thickness) with a density well above 1 g/ml.

Example 5—Composite Based on Non-Woven Paper Layers

A stack of 10 cellulose based sheets (7*10 cm Kleenex or KimberleyClark) was impregnated with 5 grams of glycerol:citric acid resin (1:1molar) which was prepared as described in Example 2. The stack was curedbetween two silicone rubber sheets placed between two ceramic tilestopped with a 2 kg stone weight for 12 hrs at 110° C. A rigid compositematerial was obtained.

Example 6—Composite Based on Woven Cotton Material

A stack of 10*10 cm of woven cotton sheets (5 layers of regular kitchentowel) was impregnated with 12 grams of glycerol:citric acid monohydrate(1:1 resin prepared as in Example 2) at a temperature of 75° C. Thestack was cured at 125° C. for 12 hrs between silicone rubber sheets,the whole being placed between two ceramic tiles under a weight of 2 kg.

A rigid porous material (0.5 cm thickness) was obtained with a densitybelow 1 g/ml.

Example 7—Composite Based on Woven Cotton Material

A stack of 10*10 cm of woven cotton sheets (10 layers of regular kitchentowel) was impregnated with glycerol/citric acid resin (1:1 molar ratio,12 grams, prepared as in Example 2), at a temperature of 75° C.

The stack was cured at 120° C. under a pressure of 10 bars in a heatpress between Teflon sheets for 12 hrs.

A stiff material with a thickness of 0.1 cm and a density above 1 g/mlwas obtained.

Example 8—Composite Based on Sawdust

Glycerol (50 grams) and citric acid monohydrate (100 grams) were heatedwith stirring at 100° C. until a clear solution was obtained after 30minutes. Epoxy-free dry sawdust (37 grams) was added in portions withstirring and the mushy paste was mixed by hand with an spatula. Thepaste was laid onto a silicone rubber sheet (12*12 cm). A secondsilicone rubber sheet was placed on top and the whole was cured at 100°C. between 2 ceramic tiles with a 2 kg stone weight on top.

A brown rigid porous density fiber board was produced, with a thicknessof 0.8 cm.

Example 9—Composite Material Based on Hemp

A 4*4 cm hemp mat of 0.8 cm thickness was impregnated with glycerolcitric acid monohydrate resin (7 grams, prepared as described in Example2) and the sample was cured between silicone rubber sheets placedbetween two ceramic tiles under a weight of 2 kg. The sample was curedat 135° C. for 12 hrs.

A porous rigid brown composite was obtained with a density below 1 g/ml.

Example 10—Composite Based on Regenerated Cellulose

Wet regenerated cellulose (12 grams) was impregnated with glycerolcitric acid monohydrate resin (prepared as in example 2) at 75° C. Thesample was cured between two silicone rubber sheets placed between twoceramic tiles under a pressure of 2 kg weight.

A smooth sheet of tanned composite (appr. 10*10 cm and 0.5 mm thickness)was obtained.

The invention claimed is:
 1. A composite material comprising from 10 to 98 wt. % of a bio-based particulate or fibrous filler and at least 2 wt. % of a polyester derived from an aliphatic polyalcohol with from 2 to 15 carbon atoms and a polyacid, wherein the polyacid comprises at least 90 wt % citric acid.
 2. The composite material according to claim 1, wherein the filler is in the form of particles, fibers, and/or random or non-random layers.
 3. The composite material according to claim 1, wherein a porous sheet-like material is used as filler.
 4. The composite material according to claim 1, wherein a particulate material, optionally in the form of a powder, dust, flakes, or chips, is used as filler.
 5. The composite material according to claim 1, wherein a plant-based filler is used, optionally a cellulosic or a lignocellulosic material, optionally at least one material selected from the group consisting of wood chips, wood flakes, sawdust, pulp, optionally pulp of recycled or unrecycled paper or other fiber pulp, and plant-derived fibers optionally comprising cotton, linen, flax, and/or hemp.
 6. The composite material according to claim 1, wherein an animal-derived filler, optionally an animal-derived fiber optionally comprising wool, hair, silk, and/or feathers is used as filler.
 7. The composite material according to claim 1, wherein the polyalcohol is selected from at least one of glycerol, sorbitol, xylitol, mannitol, 1,2-propane diol, 1,3-propane diol, and 1,2-ethane diol, and optionally comprises glycerol.
 8. The composite material according to claim 1, wherein the filler is present in an amount of at least 20 wt. %, optionally at least 40 wt. %, optionally at least 50%, and/or optionally at most 95%, or optionally at most 90%.
 9. A method for manufacturing a composite material according to claim 1, comprising combining the filler with the polyester or precursor thereof to form a composite material combination, and subjecting the combination to curing.
 10. The method for manufacturing a composite material according to claim 9, wherein the filler is combined with alcohol and acid monomers in a liquid phase, which is subjected to curing until polyester has solidified.
 11. The method for manufacturing a composite material according to claim 9, comprising combining alcohol and acid and subjecting the alcohol and acid to polymerization conditions to form a polyester in liquid form, combining the liquid polyester with the filler, and subjecting the combined polyester and filler to curing until composite material has solidified.
 12. The method according to claim 9, wherein the curing comprises subjecting the combination of filler and polyester to a temperature in a range of from 20 to 120° C., optionally from 40 to 150° C., or optionally from 80 to 130° C. and a pressure of from 1 to 100 bar, optionally from 2 to 50 bar, or optionally from 2 to 20 bar, for a period of at least 5 minutes, until composite material has solidified.
 13. A kit of parts comprising a part susceptible to degradation by a thermal load and a part comprising a composite material according to claim
 1. 14. The kit of parts according to claim 13, which is an assembly comprising a part susceptible to degradation by a thermal load and a cover surrounding said part in whole or in part, wherein the cover comprises a polyester derived from an aliphatic polyalcohol with from 2 to 15 carbon atoms and a polyacid, wherein the polyacid comprises at least 10 wt. % of tricarboxylic acid.
 15. A method for decreasing fire-propagating properties of a system comprising incorporating therein a part comprising a composite material according to claim
 1. 16. A fire-protecting cover comprising a composite material according to claim
 1. 17. A fire-protecting cover according to claim 16, which is intended for protecting a human and/or an animal body.
 18. The composite material according to claim 1, wherein the polyalcohol comprises glycerol.
 19. The composite material according to claim 1, wherein the acid is 100 wt % citric acid.
 20. The composite material according to claim 1, wherein the polyacid further comprises a dicarboxylic acid selected from at least one of succinic acid and itaconic acid. 